Turkey’s military said Wednesday it did not know the warplane it downed on the Syrian border was Russian and that it was ready for “all kinds of cooperation” with the Russian military authorities following the incident.

In a statement issued after tension surged between Ankara and Moscow and Turkey’s NATO allies appealed for calm, the Turkish armed forces also said they had made significant efforts to find and rescue the pilots after the jet was shot down.

The surviving pilot of the Su-24 bomber said earlier that no warning had been given in the incident Tuesday and the aircraft did not violate the Turkish air space, although Turkey insists that it gave 10 warnings in five minutes.

“The nationality of the plane was not known… and the rules of engagement were automatically used,” the Turkish military said in its statement.

It added that had invited Russian defence and military attaches to its Ankara headquarters to explain the incident.

It also informed Moscow’s military authorities of its readiness for “all kinds of cooperation,” the statement added.

Both Ankara and Moscow are rival players in the Syrian war and the downing of the jet stoked fears it could escalate into a wider geopolitical conflict.

President Vladimir Putin on Tuesday branded the incident a “stab in the back committed by accomplices of terrorists.”